The present invention relates to a power-assisted steering device for a vehicle, which comprises control means acting on steering means, the said control means having a transmission element such as a steering column comprising two parts which are capable of limited relative angular displacement under the action of the said control means, and auxiliary means which, in response to this angular displacement, act on the steering means in the same direction as the control means. In this device, the said auxiliary means comprise a hydraulic power system having means for pressurising a liquid and a reservoir, a hydraulic actuator acting on the said steering means, and a hydraulic distributor interposed between the power system and the actuator, the said distributor comprising an axially-stacked assembly composed of a first stator, a first rotor plate integral in rotation with one of the two parts of the transmission element, a second rotor plate integral in rotation with the other part of the transmission element, and a second stator, the said rotor plates having a series of hydraulic passages for feeding and returning the hydraulic fluid to and from the actuator by the power system via the stators.
In general, the fluid pressures in the hydraulic distributors in such power-assisted steering devices for vehicles are not in equilibrium, and as a result they have a large axial thrust, particularly when the pressure of the power system is high; this thrust is generally taken up by some form of bearing. This bearing increases the cost of the installation.
The present invention provides a device for the power-assisted steering of a vehicle, in which total or partial hydraulic equilibrium of the pressures is achieved, which makes it possible to omit the above-mentioned bearing.